Safety latch for fire doors



April 17, 1956 J, sc -r SAFETY LATCH FOR FIRE DOORS File i Feb. 2, 1953 v INVENTOR. JOE SCOTT ATTOR EYS United States Patent SAFETY LATCH FOR FIRE DOORS Joe Scott, Detroit, Mich., assignor, by mesne assignments, to National-U. S. Radiator Corporation, a corporation of Maryland pplication February 2, 1953,.Serial No. 334,501

Claims. c1. 29z 304 The present invention relates to a safety latch for furnace fire doors.

It is an object of the present invention to provide a safety latch of the class described characterized by its simplicity, the economy with which it may be produced, its efiiciency in operation, and several safety factors inherent in its construction. a

More specifically, it is an object of the present inven- .tion to provide a safety latch including a latch lever or arm movable into the path of a lug on a furnace door to prevent opening movement of the door.

Itis a further object of the present invention to provide a manual arm for swinging said latch lever or arm to release position.

It is afurther object of thepresent invention to provide in a construction of the character described a latch lever which requires manual operation to move it to release position and which restores itself to latching position upon its release.

It is a further object of the present invention to provide a latch lever of the character described adapted to be moved-by opening movement of'the door from an inoperativerange of positions to an operative or latching range of positions.

It is a'further object of the present invention to provide a safety latch for fire doors so designed that it does not require the use of springs or resilient means to perform its functions.

Other objects and features of the invention will become apparent as the description proceeds, especially when taken in conjunction with the accompanying drawings, wherein:

Figure l is a fragmentary side elevation of a furnace showing the safety latch for fire doors.

Figure 2 is a fragmentary front elevation of a furnace showing the safety latch for tire doors.

Figure 3 is a fragmentary plan view of the furnace showing the safety latch for the doors.

Figure 4 is a fragmentary side elevation of the safety latch showing the latch element in an inoperative position.

Figure 5 is a view similar to Figure 4 showing the latch being restored to operative position by opening movement of the door.

A furnace indicated generally at 10 is provided with a door frame 12 having hinged thereto a fire door 14 having a handle 16 by means of which the doorway be opened and closed. The present invention relates to latch means However, it is desirable and in some cases is a requirement by underwriters or safety regulations that the normal latch means be associated with explosion-proof latch means which prevent the fire door from being blown open upon the occurrence of an explosion within the furnace.

In accordance with the present invention a bracket 30 is mounted on the door frame 12, the bracket including two forwardly extending arms 32 and 34 having aligned openings at their outer ends for receiving a pivot pin 36. Carried by the pivot pin 36 is a bell crank indicated generally at 40 having a latch arm 42 and an actuating arm 44. As best illustrated in Figure l, the latch arm 42 has an end surface 46 which lies in the path of the lug 28 upon opening movement of the door. The latch arm 42 includes a lower corner 48 which rests upon the upper surface 24 of the striker 22. It will be observed fromFigure 1 that opening movement of the door will be arrested when the lug 28 engages the surface 46 since this will tend to rotate the latch arm 42 in a counterclockwise direction, as seen in this figure, and this is prevented by the engagement between the corner 48 of the latch arm and the striker.

With the foregoing construction in mind it is apparent that in order for the the door to be opened it is necessary for the operator to swing the latch arm 42 upwardly by moving the actuating arm 44 outwardly, while at the same time pulling the door open by means of the handle 16.

ln'some cases it is a requirement that the latch arm shall be in a position to prevent accidental opening of the door whenever the door is closed. Toaccomplish this the arms 32 and 34 of the bracket Bil are apertured to receive a pin 50 which in Figure 1 is illustrated as provided with a cotter pin 52. However, where it is a requirement that the pin 50 be not removable, it will be appreciated that the pin may be welded, riveted or otherwise permanently secured 'in position. With the pin 50 in the position shown in Figure 1 it will be observed that when the actuating arm 44 is moved outwardly the relatively heavier latch arm 42 will be arrested in a position in which it engages the pin 50 and that in this position it is adapted to return by gravity to its rest or latch position against the upper surface of the striker 22. Thus, after the door has been opened and the latch device released it will return to the position shown in Figure 1. In this position closing movement of the door merely cams the latch arm upwardly until the lug 28 reaches the illustrated position. The latch lever is restored by gravity to its latched position after inward movement of the lug 28.

However, the latch mechanism is so designed that it is automatically restored to operating or latching position ifthe pin 50 is not employed and if the latch lever has been deliberately or accidentally moved to inoperative position. Due to the relatively great weight of the latch arm 42tthere is a substantial range of movement of the'bell crank lever 40 throughout which the latch arm 42 will be restored to its latched position. However, in theabsence of the pin 50 or equivalent means, it is possible to swing'the lever 40 to the full line positionillustrated in Figure 4 at which time the relatively greater mass of the latch arm 42 tends to rock the'bell crank 40 in clockwise direction. Such movement is limited by engagement between the actuating arm 44 and the striker 22 The bell crank 40 is designed so that if placed in the inoperative range of positions and particularly in the position illustrated in Figure 4, the next opening movement of the door will restore the bell crank 40 to its operative position. For this purpose the portion 53 of the bell crank 40 adjacent the pivot pin 36 is a cam surface constituting a continuation of a surface of the actuating arm 44 and is engageable by the door lug 28 upon opening movement of the door which will swing the lever 40 from the full line position shown in Figure 4 to a position approximating the position shown in Figure 5. In Figure 5 the lever 4-0 is within its operative range of movement and is adapted to swing counterclockwise by gravity to the latched position in which the latch arm 42 rests upon the striker 22. 7

From the foregoing it will be observed that there are four possible positions of the latch lever with reference to the position of the door. In the first place, there is the safety latch position illustrated in Figure 1 in which the latch arm 54 rests upon the striker 22 in position to be engaged by the lug 28 if an explosion tends to open the furnace door. This is the normal operative position of thelatch when the furnace door is closed.

Secondly, there is the corresponding position of the latch lever when the door is open. At this time movement of the door toward closed position cams the latch arm upwardly to a position in which the lug 28 can move be neath its free end into latched position on the striker 22.

In the third place, there is the full release position of the latch lever while the door is closed, as illustrated in Figure 4. This represents a condition which is brought about only by deliberate manual manipulation of the latch lever from the position shown in Figure 1 to that shown in Figure 4. This position is useful in that it permits the furnace door to be opened by one hand; thus the operator first moves the latch lever from the position shown in Figure 1 to that shown in Figure 4, after which he opens the door merely by pulling on the handle 16. It will also be appreciated of course that this position cannot be reached so long as the pin 50 is in position. In other words, the position of parts illustrated in Figure 4 while very useful, will not be permitted if safety codes require the presence of the pin 50.

In the fourth place, it is possible to swing the latch lever to the position illustrated in Figure 4 while the door is open. There is no particular purpose in doing so however, and in this position the actuating arm 44 would prevent movement of the ing 28 to latched position on the striker 22. In other words, in this position the operator is prevented from closing the door and thus insures against an operation which might result in leaving the door in closed position but unlatched.

It will thus be seen that with the pin 50 in place, opening of the door requires the operator to swing the lever 40 clockwise by taking hold of the actuating arm 44 and at the same time opening the door by a direct pull on the handle 16. However, where safety codes do not require the presence of the pin 50 the door may be opened with one hand by first swinging the lever 40 to the position shown in Figure 4 and thereafter by opening the door by a direct pull on the handle 16. This opening movement of the door restores the lever to latching position so that when the door is next closed the lug 28 lifts the latch arm as it passes therebeneath, the latch arm returning by gravity to its latching position in engagement with the striker 22. While there is no purpose in ever swinging the lever 40 to the position shown in Figure 4 while the door is open, if it were inadvertently left in this position with the door open, the lever would prevent movement of the door to closed position and would thus prevent accidentally leaving the door closed but in unlatched position.

One side of the latch arm is concavely curved as indicated at 54 so that when it is in the position shown in Figure 1 while the door is open, closing movement of the door will cause the lug 28 to engage the concavely curved surface 54 at a small angle so as to avoid striking a severe blow against the latch lever. The concave surface 54 at the lower side of the latch arm reduces the impact effect of engagement between the latch arm and the lug 28 if the door is slammed shut and thus prevents slamming of the door from rotating the latch lever to full release position.

It will thus be seen that the safety latch is designed so that it may be employed with means positively preventing movement of the latch arm out of its operative range of movement, or alternatively, this means may be omitted and the latch arm is designed such that it will be restored to its operative range of movement by opening movement of the door whenever it has been inadvertently left in an inoperative position.

The drawings and the foregoing specification constitute a description of the improved safety latch for fire doors in such full, clear, concise and exact terms as to enable any person skilled in the art to practice the invention the scope of which is indicated by the appended claims.

What I claim as my invention is: r

l. A safety latch for fire doors in a furnace provided with an opening having a door hinged to one side thereof, a forwardly projecting striker secured to a marginal portion of the opening opposite the side thereof to which the door is hinged, :1 lug on the door extending into a position to engage the striker whenthe door is closing, the striker being shaped to cause the lug to ride upwardly thereon as the door closes, a bracket extending forwardly from the marginal opening portion of the opening above the striker, a pivot mounting on said bracket spaced forwardly from and above said striker, a lever on said pivot mounting comprising a latch arm extending downwardly and rearwardly from said pivot mounting and having a free end adapted to rest by gravity on the top of the striker forwardly of the door lug when the door is closed to prevent opening of the door, said lever being rotatable about its pivot mounting from the locking position in which the free end of the latch arm rests by gravity on the striker through an intermediate release position in which the latch arm is above the path of movement of the door lug but returns by gravity to looking position when released to a full release position in which said latch arm is retained by gravity in release position, said lever being adapted to be swung manually between such positions while said door is closed, a cam surface on said lever engageable by the door lug when the door is opened while the latch arm is in full release position to rotate said latch arm to locking position so as to lock the door closed in its'next movement to closed position.

2. A safety latch for fire doors in a furnace provided with an opening having a door hinged to one side thereof, a forwardly projecting striker secured to a marginal portion of'the opening opposite the side thereof to which the door is hinged, a lug on the door extending into a position to engage the striker when the door is closing, the striker being shaped to cause the lug to ride upwardly thereon as the door closes, a bracket extending forwardly from the marginal opening portion of the opening above the striker, a pivot mounting on said bracket spaced forwardly from and above said striker, a lever on said pivot mounting comprising a latch arm extending downwardly and rearwardly from said pivot mounting and having a free end adapted to rest by gravity on the top of the striker forwardly of the door lug when the door is closed to prevent opening of the door, said lever being rotatable about its pivot mounting from the locking position in which the free end of the latch arm rests by gravity on the striker through an intermediate release position in which the latch arm is above the path of movement of the door lug but returns by gravity to locking position when released to a full release position in which said latch arm is retained by gravity in release position, said lever being adapted to be swung manually between such positions while said door is closed, a cam surface on said lever engageable by the door lug when the door is opened while the latch arm is 'in full release position to rotate said latch arm to locking position so as to lock the door closed'in its next movement to closed position, an actuating arm extending upwardly and outwardly from said pivot mounting when said latch arm rests on said striker tion by downward movement applied to the actuating arm. t

3. A safety latch for fire doors in a furnace provided with an opening having a door hinged to one side thereof, a forwardly projecting striker secured to a marginal portion of the opening opposite the side thereof to which the door is hinged, a lug on the door extending into a position to engage the striker when the door is closing, the striker being shaped to cause the lug to ride upwardly thereon as the door closes, a bracket extending forwardly from the marginal opening portion of the opening above the striker, a pivot mounting on said bracket spaced forwardly from and above said striker, a lever on said pivot mounting comprising a latch arm extending downwardly and rearwardly from said pivot mounting and having a free end adapted to rest by gravity on the top of the striker forwardly of the door lug when the door is closed to prevent opening of the door, said lever being rotatable about its pivot mounting from the locking position in V which the free end of the latch arm rests by gravity on the striker through an intermediate release position in which the latch arm is above the path of movement of the door lug but returns by gravity to locking position when released to a full release position in which said latch arm is retained by gravity in release position, said lever being adapted to be swung manually between such positions while said door is closed, a cam surface on said lever engageable by the door lug when the door is opened while the latch arm is in full release position to rotate said latch arm to locking position soas to lock the door closed in its next movement to closed position, an actuating arm extending upwardly and outwardly from said pivot mounting when said latch arm rests on said striker whereby said latch arm may be moved to full latch position by downward movement applied to the actuating arm, said actuating arm extending downwardly and inwardly from said pivot mounting when said lever is in full release position and the door is closed in position to be engaged by the door lug to swing said lever to locking position upon opening movement of the door, said cam surface being a continuation of the surface of the actuating arm engaged by the door lug. I

4. A safety latch for fire doors in a furnace provided with an opening having a door hinged to one side thereof, a forwardly projecting striker secured to a marginal portion of the opening opposite the side thereof to which the door is hinged, a lug on the door extending into a position to engage the striker when the door is closing, the striker being shaped to cause the lug to ride upwardly thereon as the door closes, a bracket extending forwardly from the marginal opening'portion of the opening above the striker, a pivot mounting on said bracket spaced forwardly from and above said striker, a lever on said pivot mounting comprising a latch arm extending downwardly and rearwardly from said pivot mounting and having a free end adapted to rest by gravity on the top of the striker forwardly of the door lug when the door is closed to prevent opening of the door, said lever being rotatable which the latch arm is above the path of movement of the door lug but returns by gravity to locking position when released to a full release position in which said latch arm is retained by gravity in release position, said lever being adapted to be swung manually between such positions while said door is closed, a cam surface on said lever engageable by the door lug when the door is opened while the latch arm is in full release position to rotate said latch arm to locking position so as to lock the door closed in its next movement to closed position, the side of the latch arm engageable by the door lug upon closing movement of the door being longitudinally concave, the portion ofthe concave surface initially engaged by the door lug on closing movement of the door extending at a small angle to the path of movement of the lug to reduce impact forces if the door is slammed to closed position. 5. A safety latch for fire doors in a furnace provided with an opening having a door hinged to one side thereof, a forwardly projecting striker secured to a marginal portion of the opening opposite the side thereof to which the door is hinged, a lug on the door extending into a position to engage the striker when the door is closing, the striker being shaped to cause the lug to ride upwardly thereon as the door closes, a bracket extending forwardly from the marginal opening portion of the opening above the striker, a pivot mounting on said bracket spaced forwardly from and above said striker, a lever on said pivot mounting comprising a latch arm extending downwardly and rearwardly from said pivot mounting and having a free end adapted to rest by gravity on the top of the striker forwardly of the door lug when the door is closed to prevent opening of the door, said lever being rotatable about its pivot mounting from the locking position in which the free end of the latch arm rests by gravity on the striker through an intermediate release position in which the latch arm is above the path of movement of the door lug but returns by gravity to locking position when released to a full release position in which said latch arm is retained by gravity in release position, said lever being adapted to be swung manually between such positions while said door is closed, a cam surface on said lever engageable by the door lug when the door is opened while the latch arm is in full release position to rotate said latch arm to locking position so as to lock the door closed in its next movement to closed position, and a releasable pin carried by the bracket and adapted when in position to prevent movement of the latch arm to full release position and to limit it to movement between its latched and its intermediate release position.

References Cited in the file of this patent UNITED STATES PATENTS 260,355 Barr July 4, 1882 633,008 Jefiers Sept. 12, 1899 1,183,575 Longenecker May 16, 1916 

